Railway traffic controlling apparatus



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United States Patent RAILWAY TRAFFIC CONTROLLING APPARATUS.

Filed Feb. 6, 1959, Ser. No. 791,731

19 Claims. (Cl. 246-26) My invention relates to railway traffic controlling apparatus and particularly to apparatus which will give protection to traiic movements over a non-continuously track-circuited stretch of railway track. More specically my invention relates to a circuit arrangement, commonly known in the railway signaling art as a trap circuit, for a stretch of single track railway over which trains may travel in either direction, and to apparatus for controlling signals or other traic controlling devices governing the entrance of the trains into said track stretch.

In railway signaling or traic controlling systems it is sometimes impossible to provide continuous track circuits for the detection of track occupancy by a train. This problem is most often encountered at locations where a dead section occurs -in otherwise continuous track circuited territory, such as multiple track railway crossings. At such locations a trap* circuit arrangement employing a trap stick-relay is used to continue the control established by the trainl approaching such crossing until the train has fully passed beyond the crossing.

At multiple track railway crossings such as described above, the number of electrical conductors employed for the control of the trap circuit arrangement is negligible inasmuch as all of the lnecessary apparatus is close and, therefore, the length of the conductors is not too great. However, in railway block signaling territory where it is impractical or impossible to provide continuous track circuits for the detection of track occupancy by a train, such as may be encountered, for example, in localities where poor track shunting conditions exist, steel crossties are used, or the provision of continuous track circuits is economically unjustiable, the number of the electrical conductors necessary for control of a trap circuit arrangement is an importtant economic factor. Due to the distance between ythe railway signals and the corresponding relatively great length of the electrical conductors necessary for control of trap circuit apparatus located at each of the signals, it is expedient to reduce the number of required conductors to a minimum. It is accordingly one object of my invention to provide a trap circuit arrangement for use in lieu of continuous track circuits for control of a railway block signaling system for a stretch of railway track.

It is another object of my invention to provide a trap circuit arrangement for control of signals governing railway traic in both directions through a stretch of single track railway and employing only two electrical conductors between signal locations.

A third object of my invention is to provide a new and novel trap circuit arrangement for use in railway signaling system.

A further object of my invention is to provide a twoconductor trap circuit arrangement in which the said two conductors are also employed for a signal control check for the'clearng of opposing signals.

, Other objects and characteristic features of my invention will become apparent as the description proceeds.

In practicing my invention I accomplish the foregoing the side of the track so as to cooperate only with the' objects by the use of a set of batteries, at each of two opposing signal locations, which are normally connected in series with each other through the windings of an approach relay at each location. A trap stick relay is also employed Vat each of the signal locations to provide detection of occupancy of the track stretch between the locations.

I shall describe one arrangement of apparatus embodying my invention and shall then point out the novel features thereof in claims.

In the drawing there is represented by a single line a stretch of railway track extending between a first point designated by the reference character A at a first location 1 shown on the left hand side of the drawing and a second point designated by the reference character B at va second location 2 shown on the right hand side of the drawing. Trains move over the stretch in either direction as shown on the drawing by the arrow above the single line representation of the track stretch. Signals 1G Vand 2G located at locations 1 and 2, respectively, control traic movements through the track stretch between the two signals in the eastward andwestward directions, respectively.` 'Ihe two vertical lines with arrow heads in the center ofthe drawing designate the apparatus located at locations 1 and 2, respectively, employed for control of the said signals at each respective location.

Wayside devicesV or inductors designated ICV and 2CVy are located at each of the locations 1 and 2, respectively., These devices consistrof a winding or coil of a magnetizable core and are train detecting devices which detect! the passage of the ,rear end ofwa train as 'hereinafter' described. There is' also shown on the single line repre-- sentation ofthe track stretch shortsdetector trackl sections designated lT and 2T at locations 1 and 2, respectively. The limits of these track sections are designated by the short lines drawn vertically through the single line track representation and the horizontal extensions of the short lines designate in the conventional manner the track circuited'portions of the track stretch. Each of these track sections is provided with a track circuit including track relays `1TR andV ZTR for track sections' 1T and 2T, respectively, and in the manner well known in the art in which the track relays are energized and picked up only when the track sections are unoccupied by a train. a

Trains moving over the track stretch are provided on the right side of the rear end thereof with a permanent` magnet. For the purpose of simplifying the drawing, no train or its magnet is shown but it will be readily understood that wayside coils 1CV fand 2CV are located on proper train carried magnet. For example, coil 1CV is located on the north side of .the track and is thus so located to cooperate onlyl with train carried magnets of westbound trains. Similarly, coil 2CV is located on the south side of the track and is thus arranged to cooperate only with the eastbound train magnets. It is to be understood that the wayside coils 1CV and 2CV andi the train carried magnets are to be so arranged thatV theY magnets will move past the proper coils in rela'- tively close proximity thereto as the trains pass the' respective locations.

. Iwo detector relays designated lCVR and ZCVR areV shown at locations 1 yand 2, respectively. `The winding ,y of each of these relays is connected to the terminals oft its respective wayside coil 1CV or 2CV. The coils, thel relays, and the' train carried permanent magnets are selected so that, when the magnetic field of a ltrain carried permanent magnet is cut by the core of a wayside A, coil, energy is induced in the coil which 'momentarily energiies and picks up the detector relay connected to e the terminals of the wayside coil, the relays being normally released.

Extending between locations 1 yand 2 are two electrical conductors designated 3 and 4. These conductors may be the usual open line pole-supported wires or may be in underground cable as desired. There is provided at each of the llocations 1 and 2 a local and line battery designated 1B and 2B, respectively, `and an approach relay designated 1AR and 2AR, respectively. These batteries and the windings of the relays are connected in series in a manner sometimes referred to as a circulating battery circuit. This circuit may be traced from positive terminal B1 of battery 1B through the front point of contact b of relay ITSR, to be described, the front point of contact b of relay IASR, to be described, back contact b of relay ICVR, front contact b of relay ITR, conductor 3, front contact b of relay ZTR, back contact b of relay ZCVR, the front point of contact b of relay ZASR, to be described, the front point of contact b of relay ZTSR, to be described, the left hand terminal of relay ZAR through the winding of the relay to its right hand terminal, negative terminal N2 of battery 2B through the battery to its positive terminal B2, the front point of contact c of relay ZTSR, the front point of Contact c of relay ZASR, back contact c of relay ZCVR, front contact c of relay 2TR, conductor 4, front contact c of relay 1TR, back contact c of relay lCVR, the front point of contact c of relay IASR, the front point of contact c of relay lTSR, the right-hand terminal of relay IAR through the winding of the relay to its left hand terminal, negative terminal N1 of battery 1B and through the battery to its positive terminal B1. By this description it is believed apparent that relays 1AR and ZAR are normally energized in series by a circuit including batteries 1B and 2B in series.

There is shown in Ithe drawing in the conventional manner the windings only of control devices or relays lHSR and ZHSR. The control circuits to the windings of these relays are not shown as they form no part of my present invention. These relays may be controlled, for example, similar to relays RHS and LHS shown in Fig. 2b and Fig. 3 of Letters Patent of the United States No. 2,273,383 for a Remote Control System and issued February 17, 1942, to Clarence S. Snavely and Alfred B. Miller. This patent is assigned to the assignee of the present application. It is considered suflicient for the purposes of this description to state that these relays are of the well known polar stick4 type which normally have their polar contacts a in the right hand position and which contacts are controlled to their left hand or reverse position in the manner described in said Letters Patent of the United States when it is desired to control a signal to a clear position. The contacts remain or stick in the position to which last controlled until operated to their opposite position by additional controls supplied to the windings of the relays.

Relays ITER and ZTER shown in the drawings are time element relays which are employed to provide a time delay for purposes hereinafter described. Such time element relays are well known in the art and may be, for example, similar to the relay shown in Letters Patent of the United States No. 2,581,510 for Electric Relays, issued January 8, 1952, to Harry E. Ashworth and assigned to the yassignee of the present application. It is considered suicient for purposes of the present description to state that relays ITER and ZTER begin to 'operate when energy is supplied to their control windings and, after a predetermined time interval, close their front 'contacts a shown in the drawings. The purpose of employing the time element relays will become more apparent as the description proceeds.

Signals 1G and 2G shown in the drawings may be of any of the well known types but are here shown as of the color-1ight type. These signals are each shown as having two lamps, green and red, designated by the reference characters GE and RE prexed by the number of the signal with which the lamps are associated. The indications resulting from the green or red lamps being illuminated individually are clear and stop, respectively.

There is shown at location 1 a signal control relay lHR, a restoring relay IRR, an approach locking relay IASR, a trap stick relay 1TSR, and a signal control repeater relay lHPR. Similar relays designated ZHR, ZRR, ZASR, ZTSR kand ZHPR are shown at location 2. Relays ASR, lTSR, ZASR, and ZTSR are slow release relays las indicated in the conventional manner by an arrow drawn through the movable portion of the contacts of these relays in a downward direction. The purpose of making these relays slow release will be set forth hereinafter in this description.

Relay lASR at location 1 is normally maintained in a picked-up condition by a first stick circuit which extends from battery terminal B1 over contact r1 of relay lHSR in its normal position the front point of contact a of relay lASR and through the winding of the relay to terminal N1 of the battery. Relay lASR has a second stick circuit which extends from terminal B1 of the battery over back contact c of relay IAR, front contact d of relay IASR and through the winding of the relay to terminal N1 of the battery. Relay IASR has a multiple pickup circuit which extends from terminal B1 of the battery over contact a of relay lHSR in its normal position, back contact a of relay lTR and front contact a of relay 1TER in multiple, and through the winding of the relay to terminal N1 of the battery. The control circuits for relay 2ASR at location 2 being similar to that described for relay IASR no detailed description of these circuits for this relay is considered necessary.

Relay ITSR at location 1 is normally maintained in a picked-up condition by a stick circuit which extends from battery terminal B1 over front contact a of relay IAR, front contact a of relay lTSR and through the winding of the relay to terminal N1 of the battery. Relay ITSR has a rst pickup circuit which extends from terminal B1 of the battery over back contact d of relay ITR, front contact a of relay lCVR and through the Winding of the relay to terminal N1 of the battery. Relay lTSR has a second pickup circuit which extends from terminal B1 of the battery over front contact a of restoring relay lRR and through the winding of the relay to terminal vN1 of the battery. The control circuits for relay 2TSR at location 2 being similar to those described for relay lTSR no detailed description of these circuits is considered necessary.

Relay IHPR at location 1 has a pickup circuit which extends from terminal B1 of the battery over back contact d of relay ITSR, back contact b of relay IAR, front contact a of relay 1'HR and through the winding of relay lHPR to terminal Nl of the battery. Relay ZHP'R at location 2 has a similar control circuit and the tracing of this circuit is also believed not to be necessary.

Relays IHR and IRR, and ZHR and ZRR at locations 1 and 2, respectively, all have pickup `circuits controlled over conductors 3 and 4. The details of these circuits will be set forth later in the specification in a description of a specific example of the operation of the circuits and apparatus of my invention.

Signal lamp IRE of signal 1G at location 1 has an energizing circuit extending from terminal B1 of thc battery over the back point of contact a of relay IHPR and through the lament of lamp IRE to terminal N1 of the battery. 'Signal lamp 1GB of signal 1G has an energizing circuit which extends from terminal B1 of the battery over the front point of contact a of relay IHPR and through the filament of lamp 1GB to terminal N1 of thc battery. Signal lamps ZGE and ZRE of signal 2G at location 2 have similar energizing circuits to those just described for signal 1G and no detailed description of these circuits is considered necessary.

estrenos tvely, each have an energizing circuit including the back points of contacts a of relays IAS'R and ZASR, respectively. These energizing circuits will be described in more detail later in this specification in describing a specic example of the operation of my invention.

Having thus generally described above the circuits for the control of .a major part `ofthe apparatus off my invention, I will now describe fthe operation of the apparatus when a control is initiated for clearing a signal for controlling a train movement from west to east through the track stretch shown, and the operation of the apparatus as the train moves through and exits from the track stretch. v

The apparatus is shown inthe drawings in the condition it is in under normal conditions, that is when no signals are cleared and no train is in the single track stretch shown. Under these circumstances signals 1G and ZG at the West and east ends respectively of the track stretch are displaying red aspects; relays 1AR, ZAR, IASR, ZASR, ITR, ZTR, ITSR and ZTSR are all energized; and relays IRR, ZRR, IHR, ZHR, ITER, ZTER, IHPR and ZHPR are all Ideenergized. Relays 'IHSR and ZHSR both occupy their normal positions. The operator at a control point initiates a control for actuating contact a of relay IHSR to .its reverse or left hand position and lthis control is transmitted to location I to so actuate that relay. Reference is Imade to the aforementioned United States Patent No. 2,273,383 lfor a complete understanding of the operation of relay IHSR.

Relay IHSR, as stated above, is actuated and contact a of that relay moves to its reverse position opening the previously described stick circuit for relay IASR including the front point of its own contact a. Relay IASR is accordingly released. The releasing of relay IASR opens at the front points of its contacts b and c the energizing circuit for relay IAR which releases. The releasing of relay IASR also closes at the back contact points of its contacts b and c a pickup circuit for relay 1HR. This circuit may be traced from terminal B2 of battery ZB at location Z, over the front point of contact c of relay ZTSR, the front point of contact c of relay ZASR, back contact c of relay ZCVR, front contact c of relay ZTR, conductor 4, front contact c of relay ITR, back contact cof relay ICVR, the back point of contact c of relay IASR and through the winding of relay IHR to the back point of contact b of relay IASR, back contact b of relay ICVR, front Contact b of relay ITR, conductor 3, front contact b of relay ZTR, back contact b of relay ZCVR, the front point of contact b of relay ZASR, the front point of contact b of relay ZTSR, and through the winding of lrelay ZAR -to terminal NZ of battery 2B. It is thus apparent that relay IHR is picked up by a circuit including Ithe winding of relay ZAR in series with the winding of relay IHR and by energy from battery ZB -at location 2. Relay ZAR remains picked up by this circui-t.

The release of relay IAR as set forth above opens at its front 4contact a the previously described stick circuit for relay ITSR and that relay releases. The release of relays 1AR and ITSR and ythe picking up -of relay IHR closes the previously described pickup circuit for relay IHPR. Relay IHPR picks up to change the aspect of signal IG from red to green over the previously described energizing circuit for that signal including contact a f relay IHPR. Signal IG is thus cleared for allowing a train movement from West to east through the track stretch.

It will now be assumed that before a train accepts signal 1G and enters the track stretch between signals 1G and ZG, the operator decides that the signal was incorreotly cleared. A control is initiated by the operator for restoring relay IHSR .to its normal position and contact a of that relay is again closed. 'The closing of contact a of relay IHSR completes an energizing circuit for relay ITER. This circuit extends from terminal B1 of battery i. relay IASR opens lat the back point energizing circuit for relay ITER and closes at the front point of its contact a the stick circuit for maintaining relayz At the end of-the predetermined time delay periodl required for operation of relay ITER, contact a of that relay in the previously described pickup circuit for relay IA'SR is closed and relay IASR picks up.

of its contact a the IASR energized. Relay ITER now returns to its released conditionopeningthe pickup circuit for relay IASR at front contact a of relay ITER. Relay IA'SR remains;

picked up over its said stick circuit.

The picking up of relay IASR opens at'theV backf points of its contacts b and c the previously described pickup circuit for relay IHR and closes at the front points of its contacts b and c a pickup circuit for relay IRR. This circuit is similar to that descnibed for relay IHR except including the front points of contacts b andV c of relay IASR and the back points of contacts b and c of rel-ay ITSR. Relay IHR is accordingly released and relay IRR ispicked up. The releasing of relay IHR opens at its front contact a the energizing circuit for relay IHPR which in turn releases; controlling signal IG to again display its red aspect.

The picking up of relay IRR closes at the front contact a of that relay the pickup circuit for relay ITSR f which is thus energized. The picking up of relay 1-TSR opens at the back points of its contacts b and c the pickup IRR and Vcloses at its front contact circuit for relay points b and c the previously described energizing circuit for relay and picked up, respectively, in that order.

circuit for relay ITSR. However, slow release will remain up for a'suiicient period of time to allow relay IAR to pick up and close the stick y circuit for relay ITSR including front contacts a of relays IAR and its normal condition.-

l will now assume that when signal IG clears toaf green aspect, as described above, it is accepted by a train moving in the eastward direction into the track stretch IG by the train and the entrance of the train into track section 1T, ldeenergizes ITR which opens at its front contacts b andV shown. The acceptance of signal track relay c the energizing circuits for relays IHR and ZAR which release. signal of relay ITR is ,completed and relay IZTSR which in turn releases.

cuit for relay ZASR including front contact d of relay ZASR. The closing of this ystick circuit assures that.l

relay ZASR will not be released if, at this time, the

operator initiates a control for actuating relay ZHSR toot the releaseof relay ZASR at this time and under these conditions will! assure that the pickup of relay ZTSR, when the train exits f its reverse position. This prevention from the track stretch as hereinafter described,'will reset the apparatus at both locations I and Z to its normabconyr l dition.` This operation will become morefjapparent as the description proceeds.

in its normal position: the yback point of contacta of relay IASR and through` the winding of relay ITER to terminal NI of the battery; Relay ITER is thus energized and begins its timing cycle.

fThe picking up off IAR. Relays IRR and IAR are thus released Y The release I of relay IRR opens at its front contact a the pickup relay ITSR being.

ITSR. The apparatus is all now returned to if t The release of relay IHR at location I controls IG to again display its red aspect to prevent a following train entering the track stretch.l `If- -the opr section 1T, pickup circuit forrelay IASR` and maintained picked up over relay ITER to restore relay IASR l ZAR at location Z as described.:V above opens at its front contacta the stick circuitr flor.:k f

The release of relay ZAR also closes at its back contact c the second stick cir- Assuming now that the train has entered track section 2T thereby releasing track relay ZTR and its rear end is passing detector 2CV at the eastward end of track section 2T, the magnetic eld of the train carried magnet on the rear end of the train will be cut by the core of the coil 2CV thereby inducing a current in the coil and momentarily energizing relay ZCVR to cause it to close its front contact a. This actuation of relay ZCVR momentarily closes the pickup circuit for relay ZTSR including back contact d of relay ZTR and front contact a of relay ZCVR. Relay ZTSR picks up and closes its stick circuit over back contact d of relay ZTR and its own front contact a. When the train vacates track section 2T and track relay ZTR again picks up, this stick circuit is opened. However, relay ZTSR being slow release that relay will not release immediately. The closing of front contacts b and c of relay ZTR closes the series control circuit for relay 2AR and, at this time, relay 1RR at location 1. Both relays ZAR and 1RR are thus picked up. The picking up of relay 2AR closes at its front contact a the stick circuit for relay ZTSR. It is thus apparent that the slow release characteristic of relay ZTSR assures the closing of its stick circuit over front contact a of relay ZAR before relay ZTSR is released by the opening of back contact d of track relay ZTR. The apparatus at location 2 is now in its normal condition.

The picking up of relay IRR at location 1, as described above, closes the pickup circuit for relay 1TSR over the Afront contact a of relay 1RR. Relay 1TSR is thus picked up at this time opening the pickup circuit for relay IRR and closing at the front points of its contacts b and c the pickup circuit for relay 1AR in series with relay ZAR. Relay IAR picks up closing the stick circuit for relay ITSR including front contact a of relay 1AR. The slow release -feature of relay lTSR assures the establishing of this stick circuit when relay IRR opens its front contact a due to the opening of the back contact points b and c of relayV ITSR. The apparatus and circuits at location 1 are also now in their normal condition.

From the above description it is apparent that the apparatus at locations 1 and 2 operates in a similar manner for Westbound train movements and no detailed description of such train movements is considered necessary.

From this desciiptionit is apparent that with apparatus of my invention as shown in the drawings, a two conductor trap circuit or check-in, check-out signaling system is provided for a stretch of railway track over which trains may at different times travel in both directions.

Although I have herein shown and described only one form of apparatus embodying my invention, it will be understood that various changes and modilications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. A system for controlling signals governing the entrance of trains into a stretch of railway track over which trains may travel in either direction, said system comprising a single pair of conductors extending between the ends of the track stretch, a source of current and an approach relay at each end yof the stretch, a circuit including the windings of said relays connected in series with said sources of current over said conductors said sources being poled in series aiding relationship, a control device at each end of the stretch, means responsive to the actuationof the control device at one end of the stretch for deenergizing the approach relay and clearing the signal at that end of the stretch, means responsive tothe entrance of a train into the stretch for deenergizing the approach relay at the opposite end of the stretch, and means responsive to the exit of the train from the stretch for reenergizing both approach relays over said pair of conductors. Y

2. In a traic control system fora stretch of railway track including signals at the opposite ends of the stretch for governing train movements into the stretch said signals normally displaying a stop indication, the combination of, two conductors extending between the ends of the stretch; an approach relay, a normally deenergized signal control relay, a normally deenergized restoring relay, a normally energized locking relay, a normally energized trap relay, train detection means including normally open and normally closed contacts, and a source of current at each end of the stretch; a series circuit including said two conductors, the windings of said approach relays, front contact points of a pair of contacts of each locking relay and each trap relay, said closed contacts of said train detection means, and said sources of current poled in series aiding relationship; an operable control device at each end of the stretch each having a normally closed contact, a rst stick circuit for each lock ing relay including the closed contact of the control device at the adjacent end of the stretch, a stick circuit for each trap relay including a front contact of the approach relay at the adjacent end of the stretch, a second stick circuit for each locking relay including a back contact of the approach relay at the adjacent end of the stretch; means including the back contact points of said pair of contacts of the locking relay at one end of the stretch for connecting the winding of the signal control relay at said end of the stretch into said series circuit in lieu of the source of current, the winding of the approach relay, and the pair of contacts of the trap relay at said end of the stretch; means including a front contact of the signal control relay at said one end of the stretch for controlling the signal at said end to a clear indication, meansl including said closed contacts of said train detection means at said one end of the stretch for momentarily opening said series circuit when a train accepts said cleared signal, means at each end of the stretch for detecting when the rear end of a train leaves the stretch, each means having a normally open contact, a pickup circuit for each trap relay including said contact of the last mentioned means at the adjacent end of the stretch closed, a pickup circuit for the locking relay at said one end of the stretch including the normally open contact of the train detection means at said end closed; means including the back contact points of said pair of contacts of the trap relay at said one end of the stretch and said front contact points of said pair of contacts of the locking relay at said one end of the stretch for connecting the winding of the restoring relay at said end into said series circuit in `lieu of the winding of the signal control relay at that end, and a pickup circuit for each trap relay including a front contact of the restoring relay at the adjacent end ofthe stretch.

3. In combination with a stretch of railway track provided at opposite ends with signals for governing traic movements in opposite directions in the stretch, a circuit comprising two conductors extending between the opposite ends of the stretch, two sources of current and two approach relays located respectively at opposite ends of the stretch, two locking relays and two trap stick relays located respectively at opposite ends of the stretch and effective normally to connect said two sources and said two approach relays in series circuit over said two conductors with said two sources poled in series aiding relationship, two signal control relays located respective ly at opposite ends of the stretch each for controlling the signal at the adjacent end of the stretch, control means for operating said locking relays, means controlled by one of said locking relays iirst to be operated for disconnecting the source and approach relay at the adjacent end of the stretch from said two conductors and for connecting the signal control relay at said adjacent end in circuit with said conductors, means controlled by each approach relay for deenergizing the trap stick relay at the adjacent end of the stretch when the approach relay is deenergized, means controlled by each signal control relay for clearing the signal at the adjacent e'nd of the condition whereby the approach relay at the opposite end of the stretch is deenergized, rear end detection means at each end of the stretch, means controlled by the rear end detection means at said opposite end of the stretch for energizing the trap stick relay at said opposite end when the rear end of said train passes the signal adjacent that end, two restoring relays located respectively at opposite ends of the stretch, means controlled by each trap stick relay and locking relay at each end of the stretch for connecting the restoring relay at the adjacent end of the stretch in series with the approach relay and the source at the opposite end of the stretch over said two conductors when the trap stick relay and locking `relay are released and picked up respectively, and means controlled by each restoring relay for energizing the trap stick relay at the adjacent end of the stretch when the restoring relay is picked up.

4. A trap relay control arrangement for a stretch of railway track provided at opposite ends with tratiic controlling devices for governing traiiic movements in opposite directions in the stretch, said arrangement comprising, -a single pair of conductors extending between the ends of the stretch, a source of current Aat each end of the stretch, an approach relay at each end of the stretch; a series circuit including said pair of conductors, the windings of said approach relays and'said sources of current poled 'in series aiding relationship; an operable control device at each end of the stretch, means controlled by each control device for disconnecting the winding of the approach relay at the adjacent end of the stretch from said series circuit when the control device is operated, a normally energized trap stick relay at each end of the stretch, means controlled by each approach relay for deenergizing the trap stick relay at the adjacent end of the stretch when the approach relay is deenergized, means responsive to the entrance of a train into the stretch -for deenergizing the approach relay at the Vopposite end of the stretch when the train enters the stretch, and a circuit including back contacts of the approach relay and the trap stick relay adjacent one end of the stretchY for controlling the-tratiic controlling device fat that end of the stretch.

5. In a railway traffic controlling system for use with. astretch of railway track provided at opposite ends w1th signals -for governing traflic in opposite directions through the stretch, in combination, a pair of conductors extending between the ends of the stretch; a source of current, an approach relay, a normally energized locking relay, and ya normally energized trap stick relay at each end of the stretch; a series. circuit including said conductors, said sources -of current poled in series aiding relationship, thewindings of -said approach relays, and front contact points of contacts of said locking relays and said trap stick relays; a signal control relay at each end of the stretch each -for controlling the signal ladjacent its respective-end of the stretch, control means for deenergizing each locking relay, circuit means including back contact points of said contacts of one of said locking relays for connecting the signal control relay at the adjacent end of the` stretch inv circuit with said conductors, means con? trolled by each approach relay for deenergizing the trap stick relay atthe adjacent end of the stretch when the approach relay is deenergized land means controlled by each signal control relay and trap stick relay for clearing the signal at the adjacent end of the stretch when the signal energized.

control relay is energized andthe ltrap stick relay is .de-

V 6. In combination with a stretch of railway track provided atppposite ends with Signals for governing trac movements in opposite directions in the stretchftwo con# ductors extending Kbetween the opposite ends of th stretch, -two sources of current andi-two approach relays located respectively at opposite ends of the stretch, two

normally energized locking relays and two normally en` ergized .trap stick relays located respectively at opposite ends of the stretch Iand eifective normally to connect said Y two sources and said two approach relays in series circuit over said two conductors with said two sources poled in series aiding relationship, two signal control relays 1ocated respectively at opposite ends of the stretch each for controlling the signal at the adjacent end of the stretch, control means for deenergizing each said locking relay,

means controlled by each locking relay for disconnecting the source and approach relay at the adjacent end of the stretch yfrom said -two conductors and for connecting the signal control relay at said end in circuit with said conductors kwhen the locking relay is released, means controlled by each approach relay for deenergizing the trapf stick relay at the adjacent end of the stretch when the approach relay is released, means controlled by each signal control rel-ay for clearing the signal at the adjacent end of the stretchwhen the signal control relay is picked up, means controlled by the acceptance of a train of one of said signals in its cleared condition for opening one or more of said two conductors whereby the signal control relay at'the 'adjacent end of the stretch Iand the approach relay at the opposite end of the stretch are released, means controlled'by the exit of the train from the stretch for energizing the trap stick relay at the adjacent end of the stretch when the train passes the signal ad-i jacent that end of the stretch, two restoring relays lo# cated respectively at opposite ends of the stretch; means controlled by the trap stick relays for separately connecting each restoring relay in circuit with said two conductors Iand thereby in series with the approach relay and the source at the opposite end of the stretch when the trap stick relay at-said opposite end is picked up, the locking relay at the adjacent end is picked upY and the trap stick relay at the adjacent end is released; and

means controlled by each restoring relay for energizing the trap stick relay at the adjacent end of the stretchk when the restoring relay is picked up.

7. In combination with a stretch of railway track provided at opposite ends with signals for governing traffic movements in opposite directions in the stretch, two conductors extending between the opposite ends of the stretch,

two sources of current located respectively at opposite'- ends of the stretch, two approach relays located respectively at opposite ends of the stretch; two locking relays, two signal control relays, two trap stick relays andf two restoring relays located respectively at opposite ends ends of the stretch, control means for controlling each said control relay, means controlled by said locking relays and said trap stick relays for connecting said two approach relays and said two sources of current in series circuit over said two conductors with said sources poled in series aiding relationship when said two locking relays and said two trap stick relays are picked up, means controlled by each locking relay for connecting the signal4 control relay at the adjacent end of the stretch to said f two conductors in lieu of the source of current and ap proach relay at the adjacent end of the stretch when the locking relay at the adjacent end is released, means conf trolled by each approach'relay for deenergizing the trap vstick relay at the adjacent endof the stretch when -the approach relay is released, means controlled by each sigf nal control relay for clearing the signal at the adjacent' 'y end of the stretch when the signal control relay is picked l up andthe yapproach relay and the trap stick yrelay at the adjacent end are released, means controlled by the acceptance ofvatrain of a cleared one of said signals for openrelay at that end of the stretch opposite said cleared one of said signals when the train passes the signal adjacent the location of said relay, two restoring relays located respectively at opposite ends of the stretch; means controlled by the trap stick relays for connecting the restoring relay at the end of the stretch adjacent said cleared one of said signals in circuit with said two conductors and thereby in series with the approach relay and the source at the opposite end of the stretch when the trap stick relay at said opposite end is picked up, the locking relays at both ends are picked up, and the track stick relay at the adjacent end is released; and means controlled by each restoring relay for energizing the trap stick relay at the adjacent end of the stretch when the restoring relay is picked up.

8. In combination with a stretch of railway track provided at opposite ends with traffic controlling devices for governing tralic movements in opposite directions in the stretch, a single pair of conductors extending between the ends of the stretch; a source of current, an approach relay, a normally energized trap stick relay, a control relay, an operable control device at each end of the stretch; means including said pair of conductors and said sources of current for normally energizing said approach relays in series, means controlled by each control dev-ice for deenergizing the approach relay at the adjacent end of the stretch when the control device is operated, means controlled yby each control device and including the source of current at the opposite end of the stretch for energizing the control relay at the adjacent end of the stretch when the control device is operated, means controlled by each approach relay for deenergizing the trap stick relay at the adjacent end of the stretch when the approach relay is deenergized, means controlled by the entrance of a train into the stretch for deenergizing each approach relay when the train enters the stretch, and means controlled by each control relay for controlling the traic controlling device at the adjacent end of the stretch to a condition to permit a train to enter the stretch when the control relay is energized and the approach relay and the trap stick relay at the adjacent end of the stretch are deenergized.

9. A control system for controlling signals governing traffic movements in opposite directions through a nontrack-circuited stretch of railway track, said system comprising; a trap stick relay, an approach relay, a source of current, a normally deenergized signal control relay, a locking relay and a control device at each end of the stretch; a single pair of conductors extending between the ends of the stretch; means including a front contact of each respective approach relay for normally maintaining the trap stick relay at the adjacent end of the stretch energized, means including each respective control device for normally maintaining the locking relay at the adjacent end of the stretch energized; means including said sources of current, said pair of conductors, and contacts of the locking relays and the trap stick relays for normally maintaining the approach relays energized in series with each other and with both sources of current, means controlled by contacts of each respective locking relay for energizing the signal control relay at the adjacent end of the stretch in series with the approach relay and source of current at the opposite end of the stretch when said respective locking relay is deenergized, means controlled by each signal control relay for clearing the signal at the adjacent end of the stretch when the signal control relay is energized and the approach relay and the trap stick relay at the adjacent end of the stretch are deenergized, and means controlled by the entrance of a train into the stretch for deenergizing the approach relay at the opposite end of the stretch.

10. A -trap circuit for a stretch of railway track extending between a iirst location and a second location comprising, la single pair of conductors extending between said locations; a source `of energy, an approach relay,

a normally energized locking relay, a normally energized trap-stick relay, a normally deenergized signal control relay, a normally deenergized restoring relay and a control device at each said location; means for energizing each respective locking relay when the control device at the adjacent location occupies a first position, means for maintaining energized each respective trap stick relay when the relay is once energized and the approach relay at the adjacent location is energized, means including said pair of conductors and said sources of energy connected in series aiding relationship for normally energizing said approach relays in series when both locking relays and both trap stick relays are energized, means for connecting the signal control relay at the lirst location in series with the source of energy at the second location when the locking relay at the iirst location is deenergized and the locking relay and trap stick relay at the second location are energized, means for momentarily opening at least one of said two conductors when a train enters said stretch; means for connecting the restoring relay at the first location in series with the source of energy .at the second location when 'the locking relays are both energized, the trap stick relay at the second location is energized, and the trap stick relay at the tirst location is deenergized; means for energizing the trap stick relay at the first location when the restoring relay at that location is energized, means for energizing the trap stick relay at the second location when a train leaves said track stretch, a signal at the first location for governing the entrance of a train into the stretch, and means including a contact of the signal control relay at lthe first location for controlling said signal.

11. A trap circuit system for controlling signals governing the entrance of trains into a stretch of railway track over which trains may travel in either direction and including only -a single pair of conductors extending between the ends of the track stretch, said system com prising, a source of current and an approach relay at each end of the stretch, a circuit including said relays connected in series with said sources of current over said conductors said sources being poled in series aiding relationship, a control device and a signal control relay at each end of the stretch, means controlled by the con trol device adjacent each end of the stretch for disconnecting the approach relay and source of current at the adjacent end of said circuit from the circuit and connecting the signal control relay at said adjacent end in series with the approach relay and source of current at the opposite end of the circuit, a trap stick relay at each end of said stretch, a holding circuit for each trap stick relay each circuit including one of its own front contacts and a front contact of the' approach relay at the adjacent end of the stretch, control means for each said signal including a front contact of the signal control relay at the adjacent end of the stretch and back contacts of the approach relay and trap stick relay at the adjacent end of the stretch, means controlled by the entrance of a train into the stretch for momentarily opening at least one conductor of said pair of conductors, means responsive to the exit of said train from the stretch for energizing the trap stick relay at the adjacent end of the stretch, a restoring relay at each end of the stretch, means responsive to the energization of the track stick relay at the last mentioned adjacent end of the stretch for energizing the restoring relay at the opposite end of the stretch, and an energizing circuit for each respective trap stick relay including a front contact of the restoring relay at the adjacent end of the stretch.

l2. A system for controlling signals governing the entrance of trains into a stretch of railway track over which trains may travel in either direction comprising, a single pair of conductors extending between the ends of the stretch, a source of current and an approach relay at each end of the stretch, a series circuit ncluding the windings of said rel-ays connected in series with said sources of current over said conductors said sources Ibeing poled in series `aiding relationship, a control device at each end of the stretch, means responsive to the actuation of the control device at each end of the stretch for removing the source of current and approach relay at the adjacent end of Ithe stretch from said series circuit, means responsive to the actuation of the control device at each end of the stretch -for clearing the signal at the adjacent end of the stretch when the approach relay at the adjacent end is deenergized, means responsive to the acceptance of a cleared signal by a train for deenergizing the approach relay at the opposite end of the stretch, and means responsive to the exit of a train from the Stretch =for successively energizing the approach relay at the adjacent end of the stretch and the approach relay at the opposite end of the stretch.

13. A system for controlling signals governing the entrance of trains into a non-continuously track-circuited stretch of railway track over which trains may travel in either direction comprising, a single pair of conductors extending between the ends of the stretch; a source of current, an approach relay, a signal control relay, and a control device at each end of the stretch; a series circuit including the approach relays connected in series with the sources of *current over the pair of conductors said sources being poled in series aiding relationship, means responsive to the actuation of the control device at each end of the stretch for connecting the signal control relay at the adjacent end in said series circuit in lieu of the approach relay and source of current at that end, means responsive to the energization of the signal control relay at each end of the stretch and the deenergization of the approach relay at the adjacent end for clearing the signal at that end, means responsive to the acceptance of a cleared signal by a train for momentarily opening said series circuit, and means responsive to the exit of a train from the stretch for re-establishing the series circuit to its rst described condition.

14. A system for controlling signals governing the entrance of trains into a non-continuously track-circuited stretch yof railway track over which trains may travel in either direction, comprising; an approach relay, a signal control relay; a restoring relay, a trap relay, a locking relay, a control device, and a source of current at each end of the stretch; a pair of conductors extendingbetween the ends of the stretch; a series circuit normally including the pair of conductors, contacts of the locking relays and the trap relays, the windings of the approach relays, and the sources of current poled in series aiding relationship; means responsive to the actuation of each control device for deenergizing the locking relay at the adjacent end of the circuit; means responsive to the deenergization of each locking relay for connecting the winding of the signal control relay at the adjacent end in said series circuit in lieu of the winding of the approach relay and the contacts of the trap relay and the source of current at said adjacent end; means responsive to the deenergization of each approach relay for deenergizing the trap relay at the adjacent end, means responsive to the deenergization of each approach relay and the trap relay at the adjacent end and to the energization of the signal control relay at said adjacent end for clearing the signal govern` ing the entrance of trains into the stretch at that end, means responsive to the acceptance of the cleared signal by a train for momentarily opening said series circuit, means responsive to the acceptance of the cleared signal by a train for energizing the locking relay at the adjacent end of the stretch, means responsive to the deenergization of the approach relay at the exit end of the stretch for maintaining the locking relay at the adjacent end energized, means responsive to the exit of -a train from the stretch for energizing the trap relay at the adjacent end of the stretch, means responsive to the energization last mentioned trap relay for restoring said series circuit to its iirst described condition.

l5. A system for controlling signals governing the entrance of trains into a stretch of railway track in opposite directions, comprising; an approach relay, a trap relay, a normally deenergized restoring relay, a normally deenergized signal control relay and a source of current at each signal location; a single pair of conductors extending ybetween the signal locations; a series circuit over said conductors normally including the windings of the approach relay; contacts of the trap relays, and said sources of current poled in series aiding relationship; a circuit including one of its own front contacts and a contact of the approach relay at the adjacent location for normally maintaining each trap relay energized, means operating when one of said singals is to be cleared for connecting the winding of the signal control relay at that signal location in said series circuit in lieu of the cont-acts or the trap relay, the winding of the approach relay, and the source of current at said signal location; means for clearing said signal when the signal control relayat said signal location is energized andthe trap relay and approach relay at the location are denergized, means forv momentarily opening said series circuit when a train accepts the cleared signal and enters the track stretch, means for energizing'the trap relay at the exit end of the stretch when said train leaves the stretch, meansl for momentarily energizing the restoring relay at the en 1 trance end of the stretch over said conductors when the trap relay at the exit end of the stretch is energized, meansfor energizing the trap relay at the entrance endof the stretch when the restoring relay at the adjacent end is energized, and means for restoring said series circuit over said pair of conductors to its rst described condition when the trap relay at the entrance end of` the stretch is energized.

16. In a traic control system Afor a stretch of railway track including signals at the opposite ends of the stretch for governing train movements into the stretch and including at each end of the stretch first train detection means having contacts momentarily operated when a train enters the stretch and a second train detection means having contacts momentarily operated only when a train leaves the stretch, said signals normally displayinga stop indication and controllable to display a clear indication; the combination of, a single pair of conductors extending between the ends of the stretch; an approach relay, a normally deenergized signal control relay, anormally deenergized restoring relay, a normally energized trap relay, a source of energy, and a control device at each end of the stretch, means including said pair of conductors and said sources of energy poled in ,series aiding relationship for normally energizing said 'approach relays in seri, means responsive to the actuation of each control device for deenergizing the approach relay at the adjacent end of the stretch when the control device is actuated, means including said pairl gizing the trap relay at the adjacent end of the stretch f when the approach relay is deenergized, means including a contact of each said second train detection means for energizing the trap relay at the adjacent end of the stretch, means including said pair of conductors and the source of energy at each end of the stretch for energizing the restoring relay at 'the opposite end of the stretch when the control device at said opposite end is in its normal condition and the trap relay at said opposite end is deenergized, means including each trap relay for preventing energization of the approach relay at the adjacent end of the stretch when the trap relay is deenergized, and means including each restoring relay for energizing the trap relay at the adjacent end of the stretch when the restoring relay is energized.

17. In combination, a single pair of conductors extending between a tirst location and a second location; a source of energy and rst, second, and third relays at each location; a series circuit including the windings of the first relays connected in series with the sources of energy poled in series aiding relationship over the pair of conductors, means controlled by the actuation of each second relay for disconnecting the first relay and the source of energy at the adjacent location from the series circuit and reestablishing the remainder of the circuit, means controlled by the actuation of each third relay subsequent to the actuation of the second relay at the adjacent location for opening the re-established series circuit, and means controlled by each tirst relay second to be released for preventing the actuation of the second relay at the adjacent location.

1S. In a system for controlling signals governing the entrance of trains in opposite directions into a non-continuously track-circuited stretch of railway track, the combination of, a source of energy and iirst and second relays at each end of the stretch, a single pair of conductors extending between the ends of the stretch, a series circuit including the windings of the first relays connected in series with the sources of energy poled in series aiding relationship over the pair of conductors, means controlled by the actuation of each second relay for disconnecting the first relay and the source of energy at the adjacent end of the stretch from the series circuit and re-establishing the remainder of the circuit, means operating to clear each signal when the rst relay at the adjacent end of the stretch is deenergized and the second relay at said end is actuated, means operating to open the re-established series circuit when a train accepts a cleared signal, and means operating to prevent the actuation of each second relay when the rst relay at the adjacent end of the stretch is the second of the first relays to be deenergized.

19. In a system for controlling signals governing the entrance of trains in opposite directions into a stretch of railway track, said signals normally displaying a stop indication, the combination of; a source of energy, an approach relay, and a locking relay at each end of the stretch, a single pair ofv conductors extending between the ends ot the stretch, a series circuit for normally energizing both approach relays in series said circuit in cluding said conductors and said sources of energy poled in series aiding relationship, means controlled by the actuation of each locking relay for disconnecting the approach relay and the source of energy at the adjacent end of the stretch and re-establishing the remainder of the series circuit, means controlled by the actuation of each locking relay and the deenergization ofthe approach relay at the adjacent end of the stretch for clearing the signal at said adjacent end, means controlled by the entrance of a train into the stretch past a cleared signal for opening said re-established series circuit, and means controlled by the de-energization of the approach relay at the end of the stretch opposite said cleared signal for preventing the actuation of the locking relay at said opposite end.

References Cited in the tile of this patent UNITED STATES PATENTS 1,611,184 Griffin Dec. 21, 1926 1,889,450 Mersereau Nov. Z9, 1932 2,090,711 Van Horn Aug. 24, 1937 2,249,097 Van Horn July 15, 1941 2,333,974 Bell Nov. 9, 1943 2,895,042 Hailes July 14, 1959 

